Preparation and characterization of TiO2/carbon composite thin films with enhanced photocatalytic activity

Composite TiO2/carbon thin films prepared by physical vapor deposition techniques on fused silica substrates show enhanced photocatalytic activity towards decomposition of methanol to CO2 and water, as compared to pure TiO2 films of similar thickness. Raman and XRD measurements confirm that annealed TiO2 films exhibit anatase structure while the carbon layer becomes graphitic. Characteristic for the composite films is an enhanced optical absorption in the visible range. The presence of the carbon film causes a shift of the TiO2 absorption edge and modifies its grain size to be smaller. We hypothesize that the observed enhancement of photocatalytic activity is due to synergy effects at the carbon/TiO2 interface, resulting in smaller titania crystallite size and anisotropic charge carrier transport, which in turn reduces their recombination probability. (C) 2010 Elsevier B.V. All rights reserved.